Cold punching metal parts



Sept. 12, 1950 J. FRETER comruncamc mm. PARTS Filed Sept. 22. 1949 FIG 2-AXIS FIG 4- FIG 3 NVENTOR.

Patented Sept. 12, 1950 ,coijn rename METAL PARTS v RoyJJFretcr,Columbus, o m

Application September 22, 1949, Serial No. 117,163 v '1 i-clai 1 Myinvention produces in one operationa greeof hole accuracy, surfacetoughness, and finish heretoiore obtained only by two or more separateoperations.

, Where accurately shaped, highly finished holes inmetal are required,it has heretofore com-,

monly been the practice of industry to subject its,

work; pieces to three separate and distinct opera-liiOHS'-;- (1,) Aflpunching or drilling, operation.

producing a rough preliminary hole, H .(2) A second separate operationof reaming, which in: creases the accuracy of the hole and eliminatesthe taper leftby the, shear of the punch. (3) thirdseparate operationof, re-reaming or grind-, ing, whicir v further increases the accuracyand,

smoothness;

In instances not common, the piercing operation (1) above is followed bya step-like cuttingshoulder on the same apparatus, producing a re:

shearcloselybehind piercing portion.. Thereis no broaching orvplanishing of the work piece when this practice is followed. ,7

In; other instances not common, the Piercing operation is followed by aseparate operation; Such'second and separate operation-is used to.-broach and burnish the hole previously pierced, This means subjectingthe work piece to twosep-,,

arate and distinct operations.

.In. other instances not common, the piercing operation isiollowed by anenlargementof the, apparatus diameter closely behind the piercing:portion. The junction of the diameterenlargement is in the nature of.ajcurve or taper working usually in combination-with a speciallydeand-as it leaves" no excess at the hole exit, no deburring of the workpiece is required. In addition, my inventionproduces ahigher degree ofaccuracy. due tothe integral broaching process.

In view of the increasin demand'for precision holes by the metal workingindustry, the elimination of one or more ofthe operations justdescribedwill result in a great savings in time, machinery and of coursecosts. My invention ,will produce a degree of hole accuracy, finish,.and surface toughness never heretofore obtained with asingle stroke ofa machine, usinga-singleconibination tool. v

In the drawing Figurell is a plan view of an apparatus formedinaaccordance with one specific embodiment of my invention.

'7 i I 2 I I Figure 2 is a plan view of an apparatus formed inaccordance with a second specific em- 7 bodiment of thesaine presentinvention. I Figure 3 is a plan view of an apparatus formed. inaccordance with a third specific embodiment of the same presentinvention. 3 Figure l is a plan view of an apparatus formed inaccordance with a fourth specific embodiment of the same presentinvention. 1

10 I Figure lillustnates planishing bead I, broaching tooth 2, andpiercing portion 4, all integral with punch body 5. The undercut 3 iscommonly used-on breaching teeth. ,FigureZ illustrates a component typeembodi-I ment of my invention. The descriptive numerals correspond so,far asthey are common to both Figure 1 and Figure 2. For example,punch'body 5 in Figure 1 corresponds to punch body Eafin Fi ure 2- J j 1Figure 2i1lustrates the apparatus composed of" threeseparate parts; thepunch body 5a,'with internal thread 6a receives the external thread Taon lower punch body 9a. v I

Figure 2 illustrates planishing bead la, the

third separate part. In this component type embodiment of my invention,the planishing beadla is made of carbide or other similar hard a terial.Planishing bead la is slipped over shoulderz8a on lowerpunch body 901beforethe two;

partsofthe punch bodyv 5a and 9a are screwed; togethen' Shoulder 8a onlower punch body 9a. centers the planishing bead la about the axis,ofpunch,- co-axially with the piercing portion} 4a and the'broachingtooth 2a.

The component type embodiment illustratedin, Figure. 2 produces an,advantage of extra ,tool economy on production runs of relatively large1, scope because; first, it permits theuse of alongwearing material suchas carbide for the plan- 40 ishingbead, and second because it permitsthe replacement of components worn or damaged llnr-f;

cident to' such long run operations. i 5

explanation of the specific function of .m

invention will apply to both embodiments hereindesignated Figure landFigure 2. 1

To perform itsfunction this apparatus is in! serted in' a "suitable toolholder not herein 'illustrated." The-tool holder-may be a partof anymachine arrangedfor cold punching metal parts;

'Thei forcing; of the piercing portion 4 orfl iizo through a metalworkpiece produces a rough andtapered preliminary hole in the work piece.."At' he" this point a vburr is necessarily produced at t exit of thework piece.

'Thetaper in the pierced hole and the'burriats the exit of the hole areremoved by the broach-i ing tooth 2' or 2a,'which cutsmaterial'away.fror'n-f the sides of the hole. The breaching tooth 2 01i;

2a employs an undercut 3 or 3a for cuttin and curling the chips of thematerial.

The planishing bead I or la smoothes out the tool marks left by thepiercing and breaching. The planishing bead l or la also compacts themetal in the sides of the hole as itpassesthrough, producing a highlyfinished accurate hole.

It should be noted that the broaching tooth 2 or 2a is necessarily of agreater diameter than the punching portion 4 or do so that the broachingtooth 2 or 2a can engage the metal iii-the work" piece. For the samereason it is necessary that the planishing bead l or in be ofia'g'reate-r diameter than the broachingl tooth 2 or 20.

The separate embodiment of my invention shown in Figure 3 difiers fromthe embodiment shown in Figure 1 only to the extent that the integralplanishing' beadl of Figure 1 is not present in Figure 3. The embodimentshown Fig-'- ure 3 may be used where the surfacedensifica-tion and addedhole accurcy produced by the plan'i'shing bead is not required. Theundercut- 3b in the breaching tooth 2b is employed to curlthe chips ofmetal as they are cut from the hole wall. This undercut tooth, curlingmetal chips behind the piercing portion of the punch, eliminatestherelative inaccurate practice of crowding nietal ahead of a flat-facedreshearing'shoulder. The necked-in shank section l-eb, following thepiers-- ing portion, provides room for the metalchi-ps curled from thehole wallby the undercut broaching tooth.

The separate embodiment" of my inventionshown in Figure 4 differs fromthe embodiment shown in Figure 2 only to the extent that the thereforedo not claim any of such combinations.

I claim:

1. An apparatus for cold punching metal parts producing, in oneoperation, accurately sized highly finished holes with densifiedparallel sides: a punch having a piercing portion on its end, followedby a necked-in shank section for chip clearance; followed by a coaxialbroaching tooth at a slightly greater distance from the axis of punchthan the piercing edge, said broaching tooth being undercut to curl thechips of metal as they are cut from the walls of a hole of any crosssectional shape; followed by a coaxial plan.- ishing bead with a convexworking surface, at a slightly greater distance from the axis of punchthan the broaching tooth.

2. An apparatus for cold punching metal parts producing, in oneoperation, accurately sized highly finished holes with densifiedparallelsides: a punch of three component parts havinga pierc"-- ing portion onits end, followed by" a necked-in shank section for chip clearance;followed by a coaxial breachin tooth at a slightly greater distance fromthe axis of punch than the piercing edge, saidbreaching tooth beingundercut to curl the chips of metal as they are cut from the' walls of ahole of any cross sectional shape; folintegral broaching tooth 2a ofFigure 2 isnot present in Figure 4. The embodiment shown in Figure 4 maybe used where surface densificationis desired, but the added accuracyproducedby the broaching land planishing combination not required. Theremovable planishin'g head to is made of a long wearing material such ascarbide. Because of the two piece punch body construction, thisplan-ishing bead may be removed and. replaced in the event of breakageor wear. Hole wall densiflcation and increased accuracy of hole size isobtained when this embodiment is. used in" conjunction with: a standardfemale punch die.- The convex working surface of. the" pla-nishing beadlc neednot be semicircular in section, but may assume any convex shapethat will smooth and densify the hole wall. -t.

The four embodimentsof my invention herein described and illustrated arein noway limited to the production of round holes. Holes of any crosssectional shape may be formed, and theample. r I

My invention may be containedin different forms of construction fordifferent purposes, all of which come within the purview of my claimshereinafter appended. Therefore I have; de scribed and illustrated forpurposes-oi disclosure, four specific embodimentsof my invention. It isobvious that those skilled in the art may, vary the details withoutdeparting from the spirit of the invention, and therefore it is. notwished to be limited by what is herein described. .andillustrated,except as may be requiredby the claims. a

I am aware that the combination of a punch, with a supplemental cuttingshoulder is not new. I am also aware that the combination'of a punchwith a coaxial taper S8Cl3iOlfl-WOrkiIlg in conjunction with a specialfemale dia is not new. I-

lowed by a coaxial planishing bead with a con"- vex working surf-ace, ata slightly greater distance from the axis of punch than the broachingtooth; and with the body of such punch being of two separate parts toallow the mountingof a separate and removable planishing bead at thejunction of the two punch body parts.

3. An apparatus for cold punching metal parts. producing, in oneoperation, accurately sized highly finished holes with parallel sidesfapunch having a piercing portion on its end followed by a necked-in shanksection for chip clearance;- followed by a coaxial breaching tooth at aslightly greater distance from the axis of punch than the piercing edge,said broachin'g tooth being undercut to curl the chips of metal as theyare out from the walls of a hole of any cross sectional shape.

4. An apparatus for cold punching metal parts producing, in oneoperation, accurately sized highly finished holes with densifiedparallel sides: a punch of three component parts; hav ing a; piercingportion on its end followed: by a coaxial planishing" bead at a slightlygreater dis tance from the axis of punch than the" piercing edge, saidplanishing bead havin aconvex worn ing surface and functioninginc'onjunc'tion with any'standa rd female die andwith the: body of suchpunch beingof two separate parts, to allow common round hole is merelyone illustrat ve eX- 1 I the mounting of s p a e and rembvaible 1REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 1 Number Name Dateizonezj V Mullen oeu 24; 1c7 1199,715 Jenkins Jam 29'; 1878 237,439 Jenkins Feb; 8 2,369,896 Harris etal;' Feb: 20", 1 945 FOREIGN PATENTS Number I Country Date 19,994 GreatBritain cadre-.1894.

